linux-kernel - [tip:perf/core 10/17] kernel/events/core.c:9634:13: warning: 'perf_event_free_bpf

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Date: Fri, 12 Apr 2024 21:07:20 +0800
From: kernel test robot <lkp@...el.com>
To: Kyle Huey <me@...ehuey.com>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
	x86@...nel.org, Ingo Molnar <mingo@...nel.org>
Subject: [tip:perf/core 10/17] kernel/events/core.c:9634:13: warning:
 'perf_event_free_bpf_handler' defined but not used

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git perf/core
head:   93d3fde7fd19c2e2cde7220e7986f9a75e9c5680
commit: 4c03fe11b96bda60610aca77002e83f37b4a2242 [10/17] perf/bpf: Reorder bpf_overflow_handler() ahead of __perf_event_overflow()
config: arm64-defconfig (https://download.01.org/0day-ci/archive/20240412/202404122021.kE3qOoZo-lkp@intel.com/config)
compiler: aarch64-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240412/202404122021.kE3qOoZo-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202404122021.kE3qOoZo-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> kernel/events/core.c:9634:13: warning: 'perf_event_free_bpf_handler' defined but not used [-Wunused-function]
    9634 | static void perf_event_free_bpf_handler(struct perf_event *event)
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>> kernel/events/core.c:9596:12: warning: 'perf_event_set_bpf_handler' defined but not used [-Wunused-function]
    9596 | static int perf_event_set_bpf_handler(struct perf_event *event,
         |            ^~~~~~~~~~~~~~~~~~~~~~~~~~


vim +/perf_event_free_bpf_handler +9634 kernel/events/core.c

  9595	
> 9596	static int perf_event_set_bpf_handler(struct perf_event *event,
  9597					      struct bpf_prog *prog,
  9598					      u64 bpf_cookie)
  9599	{
  9600		if (event->overflow_handler_context)
  9601			/* hw breakpoint or kernel counter */
  9602			return -EINVAL;
  9603	
  9604		if (event->prog)
  9605			return -EEXIST;
  9606	
  9607		if (prog->type != BPF_PROG_TYPE_PERF_EVENT)
  9608			return -EINVAL;
  9609	
  9610		if (event->attr.precise_ip &&
  9611		    prog->call_get_stack &&
  9612		    (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) ||
  9613		     event->attr.exclude_callchain_kernel ||
  9614		     event->attr.exclude_callchain_user)) {
  9615			/*
  9616			 * On perf_event with precise_ip, calling bpf_get_stack()
  9617			 * may trigger unwinder warnings and occasional crashes.
  9618			 * bpf_get_[stack|stackid] works around this issue by using
  9619			 * callchain attached to perf_sample_data. If the
  9620			 * perf_event does not full (kernel and user) callchain
  9621			 * attached to perf_sample_data, do not allow attaching BPF
  9622			 * program that calls bpf_get_[stack|stackid].
  9623			 */
  9624			return -EPROTO;
  9625		}
  9626	
  9627		event->prog = prog;
  9628		event->bpf_cookie = bpf_cookie;
  9629		event->orig_overflow_handler = READ_ONCE(event->overflow_handler);
  9630		WRITE_ONCE(event->overflow_handler, bpf_overflow_handler);
  9631		return 0;
  9632	}
  9633	
> 9634	static void perf_event_free_bpf_handler(struct perf_event *event)
  9635	{
  9636		struct bpf_prog *prog = event->prog;
  9637	
  9638		if (!prog)
  9639			return;
  9640	
  9641		WRITE_ONCE(event->overflow_handler, event->orig_overflow_handler);
  9642		event->prog = NULL;
  9643		bpf_prog_put(prog);
  9644	}
  9645	#else
  9646	static int perf_event_set_bpf_handler(struct perf_event *event,
  9647					      struct bpf_prog *prog,
  9648					      u64 bpf_cookie)
  9649	{
  9650		return -EOPNOTSUPP;
  9651	}
  9652	

-- 
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https://github.com/intel/lkp-tests/wiki